The invention relates, generally, to Advanced Intelligent Network (AIN) systems and, more particularly, to a method and apparatus for connecting calls on physically distinct telecommunications servers in such systems.
AIN systems are generally known for providing enhanced voice and data network services. A typical AIN architecture distributes service logic, data and service assistance functions throughout the telecommunications network. AIN networks provide enhanced services such as, without limitation, voice mail, single number reach, speech recognition, call screening and the like. Typically, a call requiring enhanced services provided by the AIN activates a trigger in a central office switching system. Such triggers can be initiated when a caller goes off-hook, or according to dialing plans such as office dialing plans, individualized dialing plans, dialed feature codes or the like. Many other trigger types are available such as those used on trunk facilities or the feature buttons based on ISDN-telephone sets. Once a trigger has been set, the call setting that tigger is connected to the AIN system where appropriate call processing occurs based on the trigger and possible additional information provided by the calling party. Typically, the call is connected to a service control unit that consists of a control computer, a fault tolerant switch fabric unit and a plurality of service circuits connected to the switch fabric. The service circuits provide the AIN service capabilities such as voice announcements, dual-tone multifrequency (DTMF) receivers, text-to-speech conversion, speech recognition, mail boxes and the like. The switch fabric unit physically connects a calling party to one of the service circuits or to another party, as necessary to provide the appropriate AIN service.
In a conventional AIN architecture, a call is routed to the service control unit from a switching system as a result of the activation of a trigger (for example, the dialed directory number, call forward on busy, or the like). The control information for the call is sent to the control computer which determines the service to be performed and instructs the switch fabric unit to sequentially connect the call to one or more service circuits as appropriate for the applicable service. After the requested service has been performed the call is either completed or returned to the originating switching system.
The switch fabric units typically consist of a digital switch fabric with fully duplicated time slot interchangers such as a switch fabric using 5ESS(copyright) switching systems manufactured and sold by Lucent Technologies Inc. While such switch fabrics are extremely robust, they are also relatively expensive. Moreover, because such switch fabrics are designed to handle the traffic of a network switching system, they are not scaleable to meet the varying traffic demands of an AIN.
As a result, another conventional AIN has been developed that replaces the switch fabric unit with a plurality of physically distinct telecommunication servers consisting of personal computers having standard computer telephony hardware and interfaces. The telecommunication servers perform the routing function of the switch fabric units but are less expensive, scaleable and ultimately provide greater capacity than the switch fabric units. One problem with such distributed systems is that calls terminating at different servers cannot be connected when the need arises because the servers operate relatively independently in providing AIN service. Alternatively, hardware resources must be prereserved in order to permit inter-server connections. To eliminate these problems, the prior art uses a separate switch fabric located in front of the servers or dedicated physical interfaces between the servers to handle interserver connections. In either of these scenarios additional hardware is required, resulting in wasted resources, higher costs, lower reliability, and lower capacity.
Thus, an improved system for connecting calls on physically distinct servers in an AIN is desired.
The system of the invention makes a bridge connection between respective interfaces on physically distinct telecommunication servers such that the two ends of the bridge can be used to. connect existing calls that are terminated on each of the servers. To provide the bridge connection, a call using a standard outgoing primary rate interface (PRI) trunk on one of the servers is made through the public switched telephone network (PSTN) to an incoming PRI trunk on the other server. The servers each designate a directory number for such calls from any of the directory numbers that the PSTN associates with any of the lines terminated on that server. When a bridge connection is required, one of the servers is queried for its designated special directory number. The other server is then instructed to make a call to that number, the call carrying an encoded element on an out-of-band signal that carries information specific to the call. When the called server recognizes the incoming call by the presence of the encoded element, it answers the call. The called server then uses the encoded element to associate the bridge connection with the pending action. In this manner, calls terminating on distinct servers can be connected without the need for additional hardware.